Certain printers and other image rendering devices receive images described for a device-independent color space, convert the images to a device-dependent color space, and then render the converted images. A device-independent color space describes color as perceived by the human visual system. Examples of device-independent color space include, without limitation, CIE Lab and tristimulus XYZ.
A device-dependent color space describes color as a function of the primary colorants available to a specific image rendering device. Consider a four-colorant printer that prints with cyan (C), magenta (M), yellow (Y), and black (k) inks. Device-independent images are converted to CMYK space, and the converted images are rendered with cyan, magenta, yellow and black inks.
An image rendering device may use an inverse transfer function to determine the relative quantities of primary colorants needed to obtain a desired color in device-independent color space. For example, the inverse transfer function of a four-colorant printer might specify the relative amounts of cyan, magenta, yellow and black colorants needed to produce an Lab color.
The inverse transfer function of an image rendering device can be obtained during product development. A forward transfer function of the device may be obtained by using the device to render a grid of colors, and then mapping the colors in the grid to the colors in device-independent color space. The forward transfer function may then be inverted to produce the inverse transfer function.
Inaccurate inversion can cause color errors and artifacts in images rendered by an image rendering device. The artifacts can degrade image quality. For example, inaccurate inversion for a printer can result in color artifacts and contouring in prints.
It would be desirable to improve the accuracy of the inversion.